VCM Charts

Knock Sensor (KS) System Check:

Knock Sensor Circuit:

Circuit Description
The Knock Sensor (KS) circuit consists of two knock sensors with one wire that goes directly to the VCM. The Knock Sensor (KS) check performed by the VCM consists of monitoring CKT 496 for a voltage that is more than .64 volt and less than 3.1 volts.

If voltage is too high for 16 seconds, DTC P0328 will set. If voltage is too low for 16 seconds, DTC P0327 will set.

Chart Test Description
Number(s) below refer to circled number(s) on the diagnostic chart.

1. The first test is to determine if the system is functioning at the present time.

2. Determines 5 volts at each knock sensor and faulty knock sensor(s).

3. Determines wiring fault on CKT 496.

4. Checks continuity of circuit for grounded circuit and through process of elimination diagnoses VCM.

Diagnostic Aids
The VCM applies 5 volts to CKT 496. The 8200 ohm resistor in each knock sensor together reduces the voltage to about 2.5 volts. When knock occurs, the knock sensor produces a small AC voltage that rides on top of the 2.5 volts already applied. An AC voltage monitor, in the VCM, is able to read this signal as knock and incrementally retard spark.

If the KS system checks OK, but detonation is the complaint, refer to "Detonation/Spark Knock". Detonation/Spark Knock/Pings

NOTICE: DO NOT backprobe VCM connectors as damage to seals may occur.